1. Field of the Invention
The invention relates to a vibration damping control device for a vehicle such as an automobile or the like, and more specifically, to a vibration damping control device that controls a drive output (a driving force or a driving torque) of a vehicle employing an engine as a drive unit to damp vibrations of a vehicle body, and to the vehicle mounted with the vibration damping control device.
2. Description of the Related Art
While vibrations such as pitch/bounce vibrations and the like during the running of a vehicle are caused by a braking/driving force (or an inertial force) acting on a vehicle body during acceleration/deceleration of the vehicle or other external forces acting on the vehicle body, these forces are reflected by “wheel torques” applied to a road surface by wheels (driving wheels when the vehicle is driven) (torques acting between the wheels and the road surface on which the wheels are grounded). Thus, in the field of vibration damping control for a vehicle, it is proposed to damp vibrations of a vehicle body during the running of the vehicle by adjusting wheel torques through drive output control of an engine of the vehicle or any other drive unit of the vehicle (e.g., see Japanese Patent Application Publication No. 2004-168148 (JP-A-2004-168148) and Japanese Patent Application Publication No. 2006-69472 (JP-A-2006-69472)). In this vibration damping control of damping vibrations through drive output control, pitch/bounce vibrations that are caused to the vehicle body when a request for acceleration/deceleration of the vehicle is made or when an external force (a disturbance) acts on the vehicle body to cause fluctuations in wheel torques are predicted using a kinetic model structured assuming a mechanical model of so-called sprung vibrations of the vehicle body or so-called sprung/unsprung vibrations of the vehicle body, and a drive output of a drive unit of the vehicle is so adjusted as to damp the predicted vibrations. In the case of vibration damping control thus designed, the generation of vibrational energy is suppressed more through the adjustment of the source of a force causing vibrations than through the absorption of generated vibrational energy as in the case of vibration damping control by a suspension. Therefore, advantages such as relative swiftness of the operation of vibration damping, high energy efficiency, and the like are obtained. Further, in vibration damping control as described above, the object to be controlled is confined to wheel torques or braking/driving forces applied to the wheels. Therefore, the adjustment of control is easy.
When vibration damping control is performed through the aforementioned drive output control, the output of the drive unit is vibrationally fluctuated more often than usual to control the wheel torques in such a manner as to damp pitch/bounce vibrations of the vehicle. In this respect, when the output is vibrationally fluctuated through vibration damping control as described above in the case where the drive unit of the vehicle is a gasoline engine, the temperature of a throttle motor for adjusting the opening degree of an electronically controlled throttle that controls an intake air amount of the engine, an actuator, or a conductor thereof rises. It has been found out that the operation responsiveness of the throttle motor or the actuator may thereby deteriorate.
In the case where the gasoline engine is employed as the drive unit, the control of the intake air amount for drive output control for performing vibration damping control as described above is performed through the control of adjusting the opening degree of the electronically controlled throttle. In this control of the electronically controlled throttle, “the throttle motor” or “the actuator” is operated to displace the position or angle of a valve body of a throttle valve such that the throttle opening degree becomes equal to an opening degree for achieving an intake air amount determined according to an arbitrary method by an electronic control unit. A DC motor, a stepping motor, or the like is typically adopted as the throttle motor or the actuator. This motor or this actuator is urged by being supplied with a current while being controlled by the electronic control unit, and drives the valve body such that an actual opening degree of the throttle valve coincides with a requested throttle opening degree (a target value of the throttle opening degree) corresponding to a requested value of the intake air amount, on the basis of a value of the position or angle of the valve body detected by a throttle position sensor or a throttle opening degree sensor or a value of the air amount detected by an intake air amount sensor. In this configuration, when vibration damping control requests a vibrational drive output as described above, the intake air amount and hence the requested throttle opening degree vibrationally change as well. Therefore, when the frequency with which the position or angle of the valve body is displaced increases and especially the frequency and/or amplitude of changes in the position or angle of the valve body increase, the amount of the current per unit time and the amount of heat generation resulting therefrom increase. In consequence, the temperature of the throttle motor, the actuator, or the conductor thereof may rise. (In the case where the valve body is driven by the aforementioned motor adopted in the electronically controlled typical throttle valve, the urging current of the motor in shifting the position or angle of the valve body more drastically increases than a holding current in the case where the valve body is held at a certain position or a certain angle.) When the temperature of the throttle motor, the actuator, or the conductor thereof then rises, the operation responsiveness of the throttle motor or the actuator slows down. A deterioration in the stability of vibration damping control and a delay or shift in the phase of the vibrational displacement of the throttle opening degree may thereby be caused. In some cases, therefore, the effect of vibration damping is not sufficiently obtained.